1. Field of the Invention
The present invention relates to an ECDN protein, which is a novel steroid hormone receptor-like protein, a DNA encoding the same and processes for the production and use of this protein.
2. Description of the Related Art
As steroid hormone receptor-like proteins, there have been found and identified a group of proteins which are homologous with each other in amino acid sequence. These proteins are respondent not only to steroid hormones but also to thyroid hormones and derivatives of fat-soluble vitamins such as vitamin D metabolites and natural and synthetic derivatives thereof, retinoic acid and natural and synthetic derivatives thereof and vitamin A metabolites. These ligand-dependent transcription regulating proteins constitute a superfamily and can regulate the expression of a specific gene by binding directly to a response element of a DNA specific for stimulation by a hormone or a ligand. It has been revealed that these receptor proteins play very important roles in the development, differentiation and the maintenance of homeostasis as transcription regulating factors which regulate the expression of specific genes with the use of hormones or vitamins as ligands Evans, R. M., Science, 240, 889 (1988)!. Thus, natural and synthetic derivatives which are capable of binding to these receptor proteins and-acting as ligands have been widely studied and applied in the fields of medicine, pharmacology and agriculture.
A group of proteins seemingly belonging to the superfamily of steroid hormone receptor proteins involve a group of a number of proteins which have been produced by molecular clonings effected by hybridizations under the lowered stringency, paying attention to the homology of DNA binding domains common to the superfamily. The group of these proteins include a group of proteins called orphan receptors, the ligands specific for which have been unidentified hitherto Laudet, V. et. al., EMBO J., 11, 1003 (1992)!. It is considered that studies on the identification of the ligands specific for these orphan receptors and functions of these orphan receptors as transcription regulating factors are highly important, since novel medical and biological findings applicable to medicines and agriculture might be provided thereby. For example, it has been clarified that the ligand of retinoid X receptor (RXR), which was once regarded as an orphan receptor, is 9-cis-retinoic acid and that RXR is a receptor having an important role in transcriptional regulation Levin, A., et. al., NATURE, 359 (1992)!. It seems that in the proteins participating in the human transcriptional regulation mechanism depending on ligands, a number of receptors still remain unidentified. Therefore, it is highly meaningful to isolate and identify these receptors from the viewpoint of the application thereof to medicine and pharmacology too.